The invention relates to a method for turning off a drive device in a motor vehicle by a control device. The invention also includes a motor vehicle having a drive device, a control device for starting and turning off the drive device and a detection device for monitoring the presence of a person in the motor vehicle. For the purposes of this specification, the drive device may be an internal combustion engine, an electric motor or else a hybrid drive, for example.
If a driver leaves his motor vehicle, this per se generally does not result in an operating state of the vehicle being automatically changed thereby. The vehicle remains in the state in which the driver left the vehicle. If an internal combustion engine continues to run in this case, the vehicle produces harmful exhaust gases. In order to reduce the fuel consumption during short stopping phases, for example when stopped at a traffic light which has changed to red, a start/stop system can be provided for such situations in a motor vehicle, which system switches off an internal combustion engine if a stopping phase is detected. Since the driver usually does not leave the motor vehicle here, electrical loads of the motor vehicle, that is to say a radio or an air-conditioning system for instance, continue to be operated. In a comparable manner, an internal combustion engine of a hybrid drive is also switched off whenever it is not needed, that is to say also at the beginning of a stopping phase.
If a driver now stops the motor vehicle and then gets out of the latter, the internal combustion engine is also turned off by a start/stop system in this case. For the driver, it then seems as if the motor vehicle has already been completely turned off and the driver can depart from the vehicle for an indefinite time. However, if electrical loads having a comparatively large power requirement (for example an air-conditioning system) still continue to be operated in this case in particular, there is the risk here of the vehicle not being able to be restarted. If the motor vehicle is an electrically driven vehicle, this situation occurs particularly quickly.
In modern motor vehicles, the risk of a driver forgetting to completely turn off his motor vehicle is particularly high for two further reasons. On the one hand, a motor vehicle is no longer started in many cases with an ignition key which has to be inserted into an ignition lock and turned. Instead, only a button often needs to be pressed as the starting device for starting the motor vehicle. When getting out of a motor vehicle, the driver may therefore forget to press the button again in order to completely turn off the motor vehicle again. On the other hand, modern drive devices are particularly quiet. When at a standstill, electric motors, in particular, do not produce any noise or produce only scarcely audible noise. If a driver leaves the motor vehicle, he is therefore not reminded by noises of the motor vehicle to switch off the drive device. As already stated, this risk may also exist in a motor vehicle with an internal combustion engine if it has a start/stop system or a hybrid drive.
In order to improve the operating comfort for a driver in this case, a detection device can be provided in a motor vehicle, which detection device monitors whether the driver leaves the motor vehicle. In such a case, as soon as the driver leaves the motor vehicle after a journey, both the drive motor and the electrical loads of the motor vehicle are turned off. This increases the economy of operating the motor vehicle and simultaneously reduces the risk of the vehicle remaining still on account of a discharged battery. The signal from the detection device is used to distinguish between the presence and absence of the driver. In comparison with a start/stop system, the detection device therefore has the advantage that it is expressly detected whether the driver leaves or has left the motor vehicle.
However, such a detection device is not only advantageous. If a driver gets out of his vehicle, for example, in order to only briefly open a garage door and then drive the motor vehicle into the garage, the driver will discover in amazement that his vehicle no longer reacts when he presses on the gas pedal, for example. The driver must then operate the starting device again in order to be able to drive on.
French patent publication FR 2 928 329 describes a motor vehicle having a start/stop function. The start/stop function is interrupted while a driver is outside the motor vehicle in order to prevent inadvertent starting of the engine by another person. In this case, the start/stop function can be interrupted only if the engine has been previously switched off by the start/stop function itself.